The present invention relates to a brake control apparatus for an electric motor vehicle having a battery and a motor used therein.
Electric motor vehicles conventionally have a battery (dc power supply), an inverter for converting dc power from the battery to ac power, an ac motor driven by the ac power from the inverter, and a control section for controlling the inverter. In prior art electric motor vehicles, the inverter, which is controlled in response to a command signal from an accelerator of the vehicle, in turn controls a rotational speed and other operating parameters of the ac motor. In braking, the motor is regenerative-braked according to a command signal from an electric braking control unit, thus supplying a charging current to the battery. Japanese Patent Application Laid-Open No. 57-211904 and 61-262006, for example, discloses such a control unit for regenerative braking.
While charging of the vehicle battery during regenerative braking such as occurs in prior art electric vehicles can be a useful feature, it can also be harmful. That is, for example, when the battery is already fully charged, it can become overcharged, thereby possibly damaging it.
In view of the foregoing, it is an object of the present invention to provide a brake control apparatus for an electric motor vehicle which can control the charging current to a battery based on the charging state of the battery, thereby avoiding over-charging the battery.